According to this site:
http://lrs.ed.uiuc.edu/students/tsul...omposition.htm

The US penny was 95% copper until 1982. It also lists masses. Doing a very rough calculation, let's assume that you can extract about 2.5g of copper from each pre-1983 penny. Copper is currently trading at about $1.43/lb, or $0.0003/g. As you can see, melting down pennies for copper is nowhere near feasible for generating income. This was a surprise to me, as copper production is peaking. Perhaps in a decade or two it will be closer.